6.3. INCIDENTAL REMARK ON BLOCK DIAGRAMS

Electronic devices consist nowadays in most cases of a lot of
different circuits, each of it having a special purpose playing a special role
in the oncert of the whole device. Each of the circuits itself can
be very complicated.

To visualize the function of such devices, it would be far too
confusing if we would draw all the components and interconnections in those
different circuits at once.

Therefore nowadays more and more another method of visualization
is used: the so-called BLOCK DIAGRAMM.

Here each different circuit playing a special role is symbolized
by only a block (a rectangle carrying a special symbol or a word
explaining the function). The blocks are interconnected by lines which show the
flow of the signals or of energy from one block to the other.

fig. 38

Using this method of visualization we can draw at this stage of
explanation a block diagram of the parts of a radio which we have come to know
already.

Fig. 38 shows what we can draw up to now. Additional to the
normal blockdiagramm, we find in this drawing the type of signal, appearing
between those blocks.

If you have a closer look to the output signal of the tuned
circuit you will find, that it is exactly the signal which would leave the
transmitter of the radiostation we want to listen to.

But you should know: this drawing showing an ideal situation
Normally you will have a huge attenuation on the way from the radiostation to
the receiver, and the signal leaving the tuned circuit is very small (often less
than a milli Volt).

If we receive the signal of a radiostation very near by (let us
say a few hundred meters) this signal would be - with some luck - a few hundred
milli Volts.

A sensitive earphone can produce sound with such a low voltage,
but KEEP IN MIND: EVEN IF THE OUTPUT SIGNAL OF THE TUNED CIRCUIT IS POWERFUL
ENOUGH YOU CANNOT LISTEN TO IT BY CONNECTING AN EARPHONE
DIRECTLY.